Click Buttons Info on the author of this site Go to the Home Page Go to the Contact page Read Site Updates and latest news Go to the Utility Download Page Go to the Web Links Page View or Sign my Guest Book

CHEMISTRY : Metal Cation Identification


PROJECT TITLE: ID of STRONTIUM Cations by Precipitation Reactions
LAST UPDATE: 03-June-98
VERSION HISTORY: 1.0, 1.1, 1.2 ( Context updates)
V2.0 ( Text and formatting update - Sep-2009)


This is an account on how to detect Strontium ions in solution by simple precipitation reactions. Strontium is difficult to distinguish since it forms quite few insoluble and common precipitates. With the following set of tests it will be a guide to confirm Strontium without requiring complex procedures or sophisticated equipment.


As mentioned, the tests are simple precipitation reactions. A solution of a Strontium salt (Strontium Nitrate) was mixed with an equal ammount of another solution, which give a physical change, usually a colour change due to a precipitation of the Strontium insoluble compound.

Sr++ 2X- (aq) + 2 Na+ Y- (aq) ===> Sr++ 2Y- (s) + 2 Na+ X- (aq)
(s) Solid precipitate forming a colour change in soultion

One type of reaction is not enough, to confirm the presence of Strontium, since other metal salts may give the same results. For Example with NaOH, many metals give a white ppt., and hence one can't say that the formation of a white ppt of an unknown sample with NaOH is 100% due to Strontium cations. However the verification of 4 or 5 such tests will be enough to confirm Strontium in an unknown sample.


When some Strontium Nitrate was dissolved in water, a slight white precipitate was resulted perhaps due a slight contamination. Filtering this Strontium solution would prepare a clear solution.
In 10ml testtubes, 4mls of this clear Strontium solution was placed. To this, 1 drop of the reagent was initially added, followed by the further addition of about 2mls solution, and finally in xs. The reagents includes the following compounds all having different anions (-ve). If desired, the mixture was heated gently to increase rate of reaction. If a precipitate was formed, an xs volume of the anion (eg Hydroxide) was added to determine wether the ppt is soluble in xs reagent.
The following compounds was mixed with the Strontium salt of which 13 produced a valuable result. These are marked with an Y in the React Column .
01 Sodium Hydroxide
02 Ammonium Hydroxide
03 Sodium Carbonate Y
04 Potassium Sulphate Y
05 Sodium ThioSulphate
06 Sodium (Metabi)Sulphite Y
07 Sodium Sulphide Y
08 Sodium Fluoride Y
09 Sodium Chloride
10 Potassium Bromide
11 Ammomium Iodide
12 Potassium Iodate Y
13 Ammonium Phosphate Y
14 Sodium TetraBorate (Borate) Y
15 Sodium Salicylate
16 Sodium Benzoate
17 Tannic Acid
18 Sodium Malate sol.
19 Sodium Methanoate sol.
20 Sodium Ethanoate
21 Sodium Citrate
22 Sodium Tartarate
23 Sodium Silicate Y
24 Potassium Ferro(II)Cyanide
25 Potassium Ferri(III)Cyanide
26 Sodium Vanadate
27 Potassium Permanganate
28 Potassium Dichromate
29 Sodium Tungstate
30 Ammonium Molybdate
31 Sodium BiSelenite
32 Potassium Thiocyanate


01: Sodium Hydroxide

a) A very FAINT WHITE ppt was formed, which was insoluble in xs Hydroxide. Can be considered as no reaction.

b) No further change on heating. A very good identification test since this showed that Strontium have a solable (or slightly insoluble) hydroxide. This characteristical reaction was showed to some extent only by Strontium younger brother, hence Barium!

02: Ammonium Hydroxide

a) A very FAINT WHITE ppt was formed, which was insoluble in xs Ammonia. Can be considered as no reaction.

b) No further change on heating. As above; many metals precipitate their hydroxide from Ammonia, but Strontium failed to do this, as so does Barium!

03: Sodium Carbonate

a) A MILKY WHITE ppt was formed.

b) no further reaction on heating on standing. White Strontium Carbonate was precipitated, lime most other carbonates.

04: Potassium Sulphate

a) A WHITE ppt was immediately formed.

b) No further reaction occured

Strontium Sulphate was precipitated, again like Barium (and others such as Calcium and Lead)

05: Sodium (Metabi)Sulphite

a) A WHITE PPT was given rapidly

b) No further rection on heating or standing. White and insoluble Strontium Sulphite was precipitated. No gases were detected.

06: Sodium Sulphide

a) A WHITE ppt was formed.

b) No further reaction on heating or xs. Strontium Sulphide was precipitated as a white solid.

07: Sodium Fluoride

a) No ppt was formed until xs Fluoride was added where a WHITE ppt was formed. Could be a false result!

b) No further reaction. Not so clear but the Strontium Fluoride could have been precipitated.

08: Potassium Iodate

a) This gave a WHITE ppt insoluble in xs

b) No further reaction

The Iodate was precipitated

09: Potassium Phosphate

a) A MILKY WHITE ppt was formed

b) No reaction on heating/standing

White Strontium Phosphate precipitation.

10: Sodium Borate

a) A WHITE ppt was formed

b) No further reactions

The Borate of Strontium was precipitated as a white solid

11: Sodium Citrate

a) No reaction on the addition of the Citrate to the Strontium solution.

b) On standing for some minutes after heating, a white ppt was slowly forming. Could be a slow reaction and the Citrate was precipitated

12: Sodium Silicate

a) A MILKY WHITE ppt was formed.

b) No effect on heating or standing. Strontium Silicate was precipitated as a white solid.

13: Ammonium Molybdate

a) No reaction on the addition of the Molybdate to the Strontium solution.

b) On standing for some minutes after heating, a white/cream ppt was slowly forming. White Strontium Molybdate was precipitated.


The first indication is the lack of precipitate (or just a faint one) with Sodium Hydroxide and Ammonia.

It is further confirmed by the insoluble Sulphate and Sulphite, which will lead the choice between Barium and Strontium, the only which gives the above results. If calcium fails to produce the hydroxide (very rarely), it will also get in consideration, but Calcium will form a dense White ppt with the Tungstate

Strontium can be distinguished from Barium, because Barium will react with Tannic acid, and more noticably, with Ferro(II) Cyanide, (white) Ferro(III) cyanide (Yellow brown) and Vanadate (Yellow/orange) while Strontium does not.

Finally, Strontium gives a magnificent red flame test, used in red-coloured fire works. Thanks Tony Camilleri for the Strontium Nitrate and have a great firework feast at Luqa!!!

Metal Cation ID Section Links Chemistry Section Links